This invention relates to slack adjustment for disc brakes and it more perfectly relates to clutch control means for selectively rendering the slack adjustment effective for a spring applied disc brake for railroad cars.
Prior art disc brake operators apply spring force, or fluid pressure, to disc brakes through an axially operable pushrod that has its length automatically adjustable to compensate for wear of brake pads by selective operation of a threaded adjustment. Such an operator is disclosed, for example, in the U.S. Erdman Pat. No. 3,592,299, issued July 13, 1971. In this patent, a pushrod is retracted upon release of fluid pressure for releasing the brake for a distance sufficient for normal pad clearance by resiliency of rubber packing contained in a slot acting on the periphery of the pushrod. After this limited retraction of the pushrod, a threaded slack adjustor is activated to correct for wear of a brake pad. Such dependence upon resiliency and friction of the rubber packing has its limitations for railroad use, particularly because of changes in environment of use of the brake operator over a period of time.
An object of the present invention is to provide improved operation of disc brakes which substantially oviates one or more of the limitations and disadvantages of the described prior art systems.
Another object of the present invention is to provide an improved slack adjustable operator for disc brakes that is more positive and accurate in its compensation for wear of brake pads.
Another object of the present invention is to provide an improved slack adjustable operator for disc brakes that is simplified and less expensive to manufacture than prior art devices.